There is a trend in the semiconductor device market to provide small footprint devices without the loss of electrical performance. Small footprint devices are commonly used, for instance, in mobile communications devices such as mobile telephones and portable electronic devices.
In semiconductor device technology a combination of different structures, commonly known as edge or field terminations are used to isolate the active region of a semiconductor die from the edge of the semiconductor die to isolate parasitic effects where the edge of the semiconductor die contacts the active region. For example, structures such as Field Relief Electrodes (FREs), guard ring diffusions, field plates or a combination thereof may be used to improve the blocking voltage (BV) figure of merit for a particular device.
In semiconductor devices known field or edge termination structures are a limiting factor in reduction of the size of the device. An example of a known edge termination structure 101 is shown for example in FIG. 1, and is arranged such that the outer edge of the active device structure is defined by an isolating layer 102 on which the field relief electrode 104 is located. The semiconductor device 105 may be formed on a semiconductor substrate 106 and includes an active region 107. In addition the semiconductor device also includes a channel or guard ring 108 formed in the substrate 106.
The edge termination structure 101 is arranged between the guard ring 108 and the active region 107 of the semiconductor device 105. An isolation layer 102 is formed on the guard ring 108 and a metal layer 104 is then formed on the isolation layer 102. In addition, the metal layer 104 formed on the isolation layer 102 over the edge region 109 acts as a field plate to manipulate the electric fields in the device during operation and for example improve the blocking voltage of the device. Whilst not illustrated in FIG. 1, the metal layer 104 contacts the guard ring 108 by extending the metal layer through holes or vias in the isolation layer 102 to contact the guard ring 108. The metal layer 104 arranged over the active region 107 of the device functions as an interconnect metal for connecting external contacts of the semiconductor device to the active region.
However, the arrangement isolation layer 102 extending across the channel 108 as illustrated in of FIG. 1 consumes device area on the surface of the substrate 106 and thus limits any reduction in the device footprint.
The isolating layer 102 extends from the edge termination structure on to the guard ring 108 and through holes or vias are formed in the isolating layer 102 over the guard ring 108 to connect the field relief electrode to the guard ring 108. This arrangement consumes space on the semiconductor device and results in a larger than necessary device.
Known edge termination structures, such as the type shown in FIG. 1 are thus a limiting factor on a reduction in the size of semiconductor devices.